test(tests): added test suite

The test suite is extensive. Note that LLMs were used to aid in the development of the test suite. All LLM generated code was manually reviewed.

tests/equations/closure_dilation.cpp

@@ -0,0 +1,36 @@
+#include <catch2/catch_test_macros.hpp>
+
+#include "serif/tests/equations/fixture.hpp"
+#include "serif/tests/test_tags.hpp"
+
+namespace serif::tests::equations {
+    TEST_CASE("Equation Closure Geometry Has The Analytic Dilation Factor", tags::unit & tags::equations) {
+        Fixture f;
+        const auto rho = constant(f.density_binding.size(), 0.55), h = constant(f.enthalpy_binding.size(), 0.9);
+        const auto zero_rho = constant(rho.Size(), 0.0), zero_h = constant(h.Size(), 0.0), zero_u = f.displacement(0.0);
+        constexpr double dilation = 0.2, direction_scale = 0.07;
+        ::mfem::VectorFunctionCoefficient coefficient(3, [](const ::mfem::Vector& x, ::mfem::Vector& u) {
+            u = x;
+            u *= dilation;
+        });
+        ::mfem::GridFunction displacement(&f.displacement_space);
+        displacement.ProjectCoefficient(coefficient);
+        const auto u = f.displacement_binding.gather(displacement);
+        auto du = u;
+        du *= direction_scale / dilation;
+        PreparedClosure prepared(
+            Closure{eos::models::Polytrope{3.0, 1.5}}, f.density_binding, f.displacement_binding, f.compactification,
+            f.mapper
+        );
+        ::mfem::Vector identity, deformed, action;
+        prepared.prepare(f.state(rho, h), zero_u, f.workspace);
+        prepared.residual(f.workspace, identity);
+        prepared.prepare(f.state(rho, h), u, f.workspace);
+        prepared.residual(f.workspace, deformed);
+        prepared.apply_jacobian(f.state(zero_rho, zero_h), du, f.workspace, action);
+        identity *= std::pow(1.0 + dilation, 3.0);
+        CHECK(relative_error(deformed, identity) < 5.0e-12);
+        deformed *= 3.0 * direction_scale / (1.0 + dilation);
+        CHECK(relative_error(action, deformed) < 5.0e-12);
+    }
+} // namespace serif::tests::equations